Analysis Of The Differentially Expressed Genes During Leaf Senescence Of Chinese Flowering Cabbage By RNA-Seq

Chinese flowering cabbage(Barassica rapa var. parachinensis) is one of the important leafy vegetables with high commercial value. It begins to senesce and become yellow after harvest, resulting in quality deterioration and short shelf-life, which is one of a research topics of postharvest biology of Chinese flowering cabbage. At present, most studies aiming at the mechanisms of leaf senescence are focused on the model plants, such as Arabidopsis thaliana and rice. In addition, previous reports of the postharvest of Chinese flowering cabbage are the description of the physiological process of leaf senescence, and applicable technologies, however, there is little information about the molecular regulatory mechanisms of leaf senescence of Chinese flowering cabbage. Therefore, deepening the understand of leaf senescence of Chinese flowering cabbage and its regulation mechanisms based on the results of model plants, will provide new theoretical foundation for improving postharvest preservation technology of Chinese flowering cabbage in practice. In the present work, the differentially expressed genes during leaf senescence of Chinese flowering cabbage were analyzed by RNA-Seq. The main results are listed as follows:1. 75,651 unigenes were detected as expressed during the Chinese flowering cabbage leaf senescence using three leaf samples of different senescence stages through RNA-Seq(0 d, 2 d, 5 d after havrvest), which provides reference sequences for the analysis of the Chinese flowering cabbage transcriptome during postharvest leaf senescence.2. In total, 3,604 genes were identified as differentially expressed genes during leaf senescence. Based on the expression patterns analysis, these genes could be divided into two major groups including 1,926 up-regulated genes and 1,678 down-regulated genes. Pathway enrichment analysis revealed that certain protective activity pathways were significantly enriched in the up-regulated genes, while photosynthesis, porphyrin and chlorophyll metabolism, metabolic pathways, and carbon fixation were significantly overrepresented in the down-regulated genes.3. Among the differentially expressed genes during leaf senescence of Chinese flowering cabbage, 239 transcription factors(TFs) were identified by bioinformatics. TFs including WRKY, NAC, AP2/ERF and MYB were significantly up-regulated during leaf senescence. In addition, 801 genes involved in the signaling of eight hormones were obtained.4. 9 differentially expressed NAC genes were selected and quantitative real-time PCR were further performed to confirm their expression patterns during leaf senescence of Chinese flowering cabbage. The results showed that following leaf senescence, the transcripts of 7 NAC genes were obviously increased, while 2 NAC genes were decreased, which is consistent with the results of RNA-seq. The results indicate that the differentially expressed genes obtained by RNA-seq is reliable.